The invention relates to gas turbines, in particular for airplane engines or industrial turbines. More particularly, it relates to an assembly comprising a combustion chamber integrated with a high pressure turbine nozzle.
In a gas turbine comprising an annular combustion chamber, proposals have already been made to mount the high pressure (HP) turbine nozzle constituting the inlet stage of the turbine by connecting it mechanically to the downstream end portion of the combustion chamber (throughout this application the terms “upstream” and “downstream” are used relative to the flow direction of the gas stream through the combustion chamber and the nozzle). The assembly constituted by the combustion chamber and the HP turbine nozzle can then be supported by connection ferrules, themselves connected to inner and outer metal shrouds.
Such a disposition makes it possible to ensure better continuity for the gas flow stream at the interface between the combustion chamber and the turbine nozzle, thus enabling sealing to be provided more easily at this interface, in comparison with a disposition in which the combustion chamber and the HP turbine nozzle are separately connected to the inner and outer metal shrouds.
A combustion chamber having a turbine nozzle integrated at its downstream end portion is disclosed in French patent No. FR 2 825 787. The combustion chamber is made of ceramic matrix composite (CMC) material and the assembly comprising the combustion chamber and the sectorized HP turbine nozzle is held between the inner and outer metal shrouds by means of flexible metal connection ferrules which are sectorized so as to enable them to accommodate the relative displacements due to the large differences between the coefficients of thermal expansion of metal and of ceramic composite material.
Although integrating the HP turbine nozzle with the combustion chamber presents the above-mentioned advantages, it nevertheless also presents the following problem. The HP turbine nozzle comprises a plurality of stationary vanes situated in the gas flow stream. The turning force induced by the gas flow on the vanes is taken up by the connection ferrules which must therefore be dimensioned for this purpose, while nevertheless retaining the ability to deform when they interconnect members made of materials having coefficients of expansion that are very different.